Eighty-one patients with AO-44B3 trimalleolar ankle fractures and medium-sized posterior malleolar fragments were randomized to undergo open reduction and internal fixation (FIX, n=41) or no fixation (NO-FIX, n=40). The primary outcome was functional outcome at one year, measured by the American Academy of Orthopaedic Surgeons (AAOS) questionnaire. Secondary outcomes included radiographic osteoarthritis (OA), Olerud and Molander Ankle Score (OMAS), visual analogue scale (VAS) for pain, EuroQol-5D for general health, and reduction quality via imaging. Follow-up was conducted through one year. Overall, the results revealed no significant difference in AAOS scores at one year, though pain was slightly lower in the NO-FIX group. Radiographic OA rates and reduction quality on CT were also not significantly different. These findings suggest that open fixation does not provide short-term functional or radiological benefit for medium-sized posterior fragments.